Investigation into the effect of transformer oil on polymers

Several thermoplastics and an epoxy were exposed to a variety of conditions to determine the effect of chemical environment on the materials. Weight gain measurements of the samples were made afker exposure to low humidity, ambient air, 90°C air, ambient transformer oil, and 90°C transformer oil. Two materials that performed well in these tests were polyetherimide (Ultem) and amine cured bisphenol-A epoxy. It was found that Noryl, a thermoplastic combination of high impact polystyrene and polyphenyleneoxide, was unsuitable for use in transformer oil, as it suffered substantial physical degradation. Polystyrene and high impact polystyrene (rubber modified polystyrene) performed poorly in both ambient and 90° transformer oil tests, with the rubber modified material exhibiting a much greater weight gain. Both high and low density polyethylene also showed large weight gains in hot transformer oil.